I think they just can't be bothered. They know that if they try out an do the hype of their competitors they're going to lose. Between the first anouncement of Nextbox games and the first showing of some real PS4 game.

They know that if they make one big conference it will just be overshadowed so they're spliting up, one focus on distribution, sales figures and analytics, and another for Wii U games, another for 3DS. Maybe another small Nintendo Direct or two.

Nintendo are trying to break up their news and deliver different presentation for what each group of people wants. Then after E3 they can start building apon what they announced and building hype. They just need to ride the competitor product release wave out, and then during the period where there is no games for Nextbox and PS4, they need to start pumping out the titles then.

"In this industry revolutions don't need to be original or innovative, they just need to set the new standard.":)